The present invention relates to a procedure for carrying out biotechnological processes that involve the microbial evolution of gas and that take place in reactors containing granular carriers or particles which support growth of microorganisms. The present invention further relates to equipment for carrying out the procedure in a reactor vessel provided with liquid feed and discharge and with means for the taking off and, if appropriate, the feeding in of gas.
Numerous biotechnological processes take place with the evolution of gas. Methane (CH.sub.4) is produced, for instance, in anaerobic degradation processes, and carbon dioxide (CO.sub.2) is formed in aerobic fermentation processes. Another example of bioreactions which proceed with gas evolution is bacterial denitrification, wherein nitrate is degraded in the presence of suitable bacteria and organic substances that act as indirect reducing agents under low-oxygen or oxygen-free reaction conditions.
For carrying out these react columnar fixed-bed reactors are frequently used that permanently contain a particulate carrier ("packing") on which growth of bacteria is supported and on which the bacterial reaction takes place. But problems arise when these reactors operate, particularly with increasing reactor size, due to the evolution of gas associated with the bioreaction. The gas formed is released only with delay from the where the growth is sustained; as the reaction proceeds, the delayed release of gas can lead to partial blocking of the active surface occupied by bacteria, and to an increase in the filtration resistance, so that the throughput in the reactor is neither at its optimum level nor at constant rate.
These phenomena have been investigated in more detail for denitrification in fixed-bed reactors where the organic substrate is metered into the nitrate-containing water flowing in or is made available by diffusion out of plastic packing. Nitrogen gas is evolved in the bacterial reaction, and problems arise with the release of the gas from the packed bed occupied by bacteria.